1. Field of the Invention
The present invention relates to an apparatus and a method for monitoring a battery pack, and more particularly to an apparatus and a method for monitoring a battery pack for accurately calculating an actual discharging or charging capacity of a secondary battery, which depends on temperature, so that the battery pack can be maintained and used in an optimum condition.
2. Description of the Prior Art
Typically, chargeable/dischargeable secondary batteries undergo conversion between chemical energy and electrical energy through electrochemical reactions in which internal active materials oxidize/reduce due to charging/discharging. Performance of the secondary batteries is affected by charging method, discharging depth, temperature during storage and service, load level, number of charging/discharging, and the like. Recent developments of secondary batteries are moving toward lithium ion batteries, lithium polymer batteries, or fuel cells, which have a high energy density and a small mass and are used as industrial, automobile, portable, or mobile power supplies.
Secondary batteries are generally classified into battery cells (also known as bare cells) and battery packs. The bare cells are simply adapted to be charged/discharged without any circuit mounted thereon. The battery packs include a bare cell and various protective and control circuits mounted on the bare cell and are packaged according to the external systems where the battery pack is used.
The circuits mainly control charging/discharging of the secondary batteries and are interrupted, when the secondary batteries are overcharged/over-discharged, to extend the life of the secondary batteries and to protect users from dangerous situations. Recently, monitoring systems are used to more accurately inform external systems of the remaining discharging capacity of battery packs.
However, conventional battery packs or monitoring systems calculate a discharging capacity simply based on a present voltage or current of bare cells and cannot inform external systems of the exact discharging capacity, which depends on temperature.
For example, when a battery pack is fully charged at room temperature and then used at a lower temperature, an external device displays remaining capacity data, which has been calculated based on the lower temperature. A remaining discharging capacity displayed at the lower temperature is smaller than an actual fully charged capacity. However, the remaining capacity data calculated based on the lower temperature is still displayed even when the battery back is again used at room temperature, although the remaining capacity must be updated based on the present temperature. As a result, the exact battery pack capacity conforming to the present temperature is not displayed.
In addition, when a battery pack is fully charged at room temperature and used at the same temperature, an external system displays remaining discharging capacity data, which has been calculated based on the present temperature. However, the remaining capacity data calculated based on room temperature is still displayed even when the battery pack is used at a lower temperature, although the remaining capacity must be updated based on the present temperature (lower temperature). As a result, the exact battery pack capacity conforming to the present temperature is not displayed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.